Warren Buffett's longtime lieutenant gained $300 million in past year; Berkshire Hathaway shares up 28% since last February. Called for ban on credit default swaps: "It isn't as though the economic world didn't function quite well without [them]." Omaha native studied math at U. of Michigan, dropped out to serve as meteorologist in Army Air Corps. Then Harvard Law. Began investing with Buffett after pair met at a dinner party 1959. Known for pragmatic, researched approach to investing. Helped persuade Buffett to back Chinese electric car company BYD in 2008; original $232 million Berkshire investment now worth almost $2 billion.